In a broadband wireless access system, a mobile station can request an uplink bandwidth in accordance with a random access mode of FIG. 1. A base station simultaneously supports a general five-step mode 110 to 150 and a three-step mode 110, 140 and 150 corresponding to a fast access mode. The five-step mode can be used independently from the three-step mode, and can substitute for the three-step mode.
In case of the three-step mode, the mobile station transmits a bandwidth request indicator including uplink bandwidth request information (MS ID, request size, etc.) (110). The base station which has received the indicator from the mobile station allocates uplink resources to the mobile station (140). The mobile station transmits data through the allocated region (150). At this time, the mobile station can transmit additional uplink bandwidth request information.
In case of the five-step mode, the mobile station transmits a bandwidth request indicator (110). The base station which has received the indicator from the mobile station allocates uplink resources for transmitting a bandwidth request (BW-REQ) message to the mobile station (120). The mobile station transmits the bandwidth request (BW-REQ) message through the allocated region (130). The base station which has received the bandwidth request (BW-REQ) message from the mobile station allocates uplink resources to the mobile station (140). The mobile station transmits data through the allocated region (150). At this time, the mobile station can transmit additional uplink bandwidth request information.
In the broadband wireless access system according to the related art, after transmitting the bandwidth request indicator, the mobile station cannot predict whether the bandwidth request indicator has normally been transmitted to the base station or whether the used code has been repeated, until the mobile station receives an uplink grant message or a contention-based reservation timer of the mobile station reaches time-out. Accordingly, if the mobile station does not receive any uplink grant message until the corresponding timer ends, the mobile station retransmits the bandwidth request indicator. Namely, in the broadband wireless access system according to the related art, the mobile station has no option but to wait without taking any action until the corresponding timer ends. In view of the mobile station intended to request a bandwidth of an uplink to transmit real-time traffic, such a wait time is too long and may be regarded as the unnecessary.